1. Field of the Invention
The present invention relates to a blower having an axial fan driven by a drive source arranged upstream the fan, and an integrally molded assembly to support the drive source, a shroud enclosing the axial fan, and a protective net adapted for preventing either a person from inserting his fingers into the blower or foreign materials from entering the blower from the upstream side of the axial fan. More particularly, the present invention relates to an air blower adapted for use in supplying heat exchanging devices of an automobile, such as a radiator or a refrigerant condenser for the automobile climate control system, with a flow of air. The present invention may be equivalently applicable to a fan having a lower gas discharging power.
2. Description of the Related Art
A typical conventional blower is shown in FIGS. 7 and 8. The conventional blower is provided with an axial fan 100, a protective net 101 arranged either for preventing a person's finger or fingers from entering the axial fan during the rotation thereof or for preventing foreign material from entering the blower, and a shroud 102 for enclosing the axial fan. The protective net 101 and the shroud 102 are both made of resin material, and are formed as an integrally molded assembly in order to reduce the manufacturing and assembling cost of the molded assembly.
When the axial fan 100 of the blower is driven, an air flow is generated so as to enter the blower not only through an air intake port in the axial direction but also through a region circumferentially extending around the air intake port. All of the air entering the blower is discharged as blown air through an air outlet of the blower.
In order to permit the air to easily enter the blower, the protective net 101, which is located at upstream the axial fan 100 and is formed integrally with the shroud 102, is arranged so as to be axially spaced apart from the shroud 102. Thus, the protective net 101 is supported by a number of support ribs 103 extending from the end of the shroud 102 toward the air intake port of the blower. Thus, a number of openings are defined by the support ribs 103 between the protective net 101 and the shroud 102 in such a manner that the openings are circumferentially juxtaposed. Accordingly, air can flow into the blower through the openings of the support ribs 103 so as to be mixed with the air flowing into the blower through the above-mentioned air intake port. Namely, the arrangement of the support ribs 105 is contrived so as to permit the air to pass through the openings of the support ribs 103 to thereby be smoothly mixed with the air entering through the air intake port of the blower.
The protective net 101 is constructed so that the blowing performance of the blower is not reduced due to an existence of the net 101 and so that the manufacturing cost of the protective net 101 can be lower. Thus, the protective net 101 is provided with a plurality of stays 105 having the above-mentioned support ribs 103 arranged so as to provide an interconnection between a support bracket 104 and the above-mentioned shroud 102, and a plurality of annular ribs 106 extending annularly around the air intake port so as to mutually connecting the respective stays 105.
The support bracket 104 arranged adjacent the air intake port supports a drive source driving the axial fan on the side of the air intake port.
With the above-mentioned construction of the conventional blower, the support ribs 103 are manufactured by a molding method in which they are integrally molded with the shroud 102 and the protective net 101. Therefore, in order to allow a molded assembly of the protective net 101, the shroud 102, and the support ribs 103, i.e., a molded shroud assembly to be readily removed from the molding dies during the molding process, an inner circumference of the support ribs 103 must be designed so as to have a diameter equal to that of the shroud 102. Consequently, a spacing between the edge of the axial fan 100 and the inner circumference of the support ribs 103, designated by "B" in FIG. 7 must be very small and results in an increase in noise generated by the air flow passing through the small space "B".
More specifically, since respective openings of the support ribs 103 must be small from the viewpoint of the afore-mentioned protecting purpose, a number of support ribs 103 are provided in a juxtaposed arrangement in the circumferential direction around the air intake of the blower, and accordingly, the provision of many support ribs 103 makes the sound louder when the air flows across the support ribs 103, Thus, the conventional blower has such defect in that the noise generating during the operation of the blower is loud.